This study had a 2-group pre-post quasiexperimental design and was conducted in 2 selected areas of Ubon Ratchathani province, Thailand. The objective was to evaluate the extent to which the surveillance system that was developed helped in drowning prevention. The development process involved extensive participation from the community. System efficiency was evaluated, and the drowning rates were compared. The system demonstrated 82.8% system sensitivity and 87% positive-predictive value. There were 90.0% rescues with no injury during the study period. The relative risk of drowning injury suggests that the control area was at 5.6 times more at risk for drowning injury than the intervention area (95% CI = 1.58, 20.12). Local knowledge and participation from the community were found to be key issues in the success of the surveillance system, and such systems can be applied to other areas with similar problems.